Electromyographic Ratio Research Articles

Using Electric Stimulation of the Spinal Muscles and Electromyography during Motor Tasks for Evaluation of the Role in Development and Progression of Adolescent Idiopathic Scoliosis.

Introduction: The role of the spinal muscles in scoliogenesis is not fully substantiated. Do they act scoliogenic (inducing scoliosis) or counteract scoliosis in adolescent idiopathic scoliosis (AIS)? In this study, we will examine this by using selectively placed Transcutaneous Electric Stimulation (TES) combined with a cinematic radiographic technique and by performing electromyographic (EMG) evaluations during various motor tasks. Method: This is a cross-sectional study of subjects with small-curve AIS. Using cinematic radiography, they were evaluated dynamically either under electrical stimulation or when performing motor tasks of left and right lateral bending and rotation whilst measuring the muscle activity by EMG. Results: Forty-five patients with AIS were included as subjects. Five subjects volunteered for TES and six subjects performed the motor tasks with EMG. At the initial visual evaluation, and when stimulated with TES, the frontal plane spatial positions of the vertebral bodies showed discrete changes without an apparent pattern. However, analyzing the spatial positions when calibrated, we found that the spinal muscles exert a compressive 'response' with a minor change in the Cobb angle (CA) in small-curve AIS (CA = 10-20°). In larger curves (CA > 20°), TES induced a 'larger deformity' with a relative four-fold change in the CA compared to small-curve AIS with a ratio of 0.6. When evaluating local amplitude (peak) or cumulative (mean) EMG signals, we were unable to find consistent asymmetries. However, one subject had rapid progression and one regressed to a straight spine. When adding the absolute EMG ratios for all four motor tasks, the subject with progression had almost 10-fold less summed EMG ratios, and the subject with regression had more than 3-fold higher summed EMG ratios. Discussion: Based on these findings, we suggest that the spinal muscles in small-curve AIS have a stabilizing function maintaining a straight spine and keeping it in the midline. When deformities are larger (CA > 20°), the spine muscle curve exerts a scoliogenic 'response'. This suggests that the role of the muscles converts from counteracting AIS and stabilizing the spine to being scoliogenic for a CA of more than 20°. Moreover, we interpret higher EMG ratios as heightened asymmetric spinal muscle activity when the spinal muscles try to balance the spine to maintain or correct the deformity. When progression occurs, this is preceded or accompanied by decreased EMG ratios. These findings must be substantiated by larger studies.

Electromyography of paraspinal muscles during self-corrective positions in adolescent idiopathic scoliosis.

Self-corrective exercise is commonly used in the training protocol of patients with adolescent idiopathic scoliosis (AIS). The muscle activation pattern during symmetrical and overcorrection exercises is then explored to guide the treatment. To compare the paraspinal muscle activity during three self-corrective positions and the habitual standing in AIS. Thirty-three adolescents with double curved scoliosis were examined. The curve type and Cobb's angle were determined from their whole spine X-ray. They adopted habitual standing, symmetrical correction and two overcorrected positions (O1 and O2). The surface electromyography (EMG) was monitored on both sides of paraspinal muscles at the apex areas of scoliotic curves. The EMG ratio between sides was inferred as the corrective effect. All three self-correction positions produced greater EMG ratios compared with the habitual standing. The greatest EMG ratios were observed during the O1 position at the thoracic curve and the habitual standing at the lumbar curve. Participants with different subtypes of curves exhibited similar patterns of EMG ratios. From the biomechanical viewpoint, all three self-corrective positions possibly provided therapeutic effects for the scoliotic body regardless of the subtype of scoliosis curves. The O1 position seemed to be most effective for the adjusting activation of thoracic paraspinal muscles. The symmetrical corrective position is otherwise recommended for adjusting the lumbar muscle activation.

Women with migraine presents similar altered performance in the craniocervical flexion test than women with chronic nonspecific neck pain: An observational study

BackgroundAlthough patients with migraine show cervical muscle impairments previous studies investigating motor performance have not characterized the sample of patients with migraine according to the presence/absence of neck pain complaints. ObjectiveTo verify if there are differences in the clinical and muscular performance of the superficial neck flexors and extensors during Craniocervical Flexion Test in women with migraine, considering the presence or absence of concomitant symptoms of neck pain. MethodsThe cranio-cervical flexion test performance was assessed by its clinical stage test and by the surface electromyographic activity of the sternocleidomastoid, anterior scalene muscles upper trapezius and splenius capitis. It was assessed in 25 women with migraine without neck pain, 25 women with migraine and neck pain, 25 women with chronic neck pain and 25 pain-free control women. ResultsPoorer performance of the cervical muscles was found during the execution of the cranio-cervical flexion test, in addition to higher muscle activity, especially in the sternocleidomastoid, splenius capitis, and upper trapezius muscles in the neck pain, migraine without neck pain, and migraine with neck pain groups in comparison with the results obtained for healthy women in the control group. No difference was observed between the groups of women experiencing pain. Analysis of the extensor/flexor muscle electromyographic ratio showed that there was no difference between the groups. ConclusionPoor cervical muscle performance was observed in both women with chronic nonspecific neck pain and women with migraine regardless of the presence of neck pain.

Electromyographic activities of the jaw and facial muscles in subjects with different vertical skeletal patterns and breathing modes.

Mouth breathing (MB) can affect morphological changes in the craniofacial structures, electromyography is widely used for quantitative analysis of muscle function. The aim was to evaluate the electromyographic (EMG) activities of the anterior temporalis (TA), masseter muscle (MM), orbicularis oris superior (OOS) and mentalis muscle (MT) in children with different vertical skeletal patterns and breathing modes during rest and various functional mandibular movements. BioEMG III was used to measure the variations in EMG activities of TA, MM, OOS, and MT in 185 subjects aged 6-12 years during continuous clenching, rest, maximal intercuspation, lips closed lightly and swallowing. The results of logistic regression analysis showed that the model with vertical skeletal patterns as the dependent variable was ineffective (p=.106), while the model with breathing modes as the dependent variable was effective (p=.000). When considering both vertical skeletal patterns and breathing modes, the following significant differences were found. (1) In the normal-angle group, the EMG ratio in OOS with lips closed lightly of MB was significantly higher than NB (p=.005). (2) In the low-angle group, EMG ratios in TA and MM during the swallowing of MB were significantly lower than NB (p=.020, p=.040, respectively). (3) In the high-angle group, EMG ratios of MB were significantly higher in MT during continuous clenching, rest, lips closed lightly and swallowing (p=.038, p=.036, p=.005, p=.028, respectively), and OOS with lips closed lightly compared to NB (p=.005). Breathing modes and vertical skeletal patterns interacted to alter maxillofacial EMG activities, with breathing modes having a greater effect.

Broader Estimates of Gastrocnemius Activity Generated a More Representative Cocontraction Index: A Study in Pediatric Population.

The electromyography (EMG) cocontraction index (CCI) given by the antagonistic/agonistic Root Mean Square (RMS) amplitude ratio of the same muscle is a qualified biomarker used for spastic cocontraction quantification and management in cerebral palsy children. However, this normative EMG ratio is likely subject to a potential source of errors with biased estimates when measuring the gastrocnemius plantar flexors activity. Due to the uneven distribution of electrical activity within the muscle volume, cocontraction levels can be misestimated, if EMGs are obtained from the sole traditional bipolar sensor location recommended by SENIAM. This preliminary study, on 10 healthy children (mean age 10 yr), investigated whether surface EMG detected proximally and distally via two pairs of bipolar electrodes, within the medial gastrocnemius (MG), provides a significant difference in CCI estimates during non-dynamic (isometric dorsiflexion) and dynamic (swing phases of gait) conditions. Gait cycles were extracted from Inertial Measurement Unit sensors. Medial gastrocnemius activity was greater distally than proximally during plantar flexion when it acts as an agonist (~24±18%) and it was greater proximally during dorsiflexion (~23±9%) when it is acting as an antagonist. As a direct consequence, CCI estimates from the conventional sensor location were significantly different (~36%) from the CCIs computed by considering broader MG regions. This difference arose in all subjects during isometric efforts and in two of 10 healthy children during the swing phase of gait who presented cocontraction patterns (p<0.05). EMG bipolar sampling encompassing proximal and distal gastrocnemius muscle regions may reduce bias in CCI computation and provide a more representative and accurate cocontraction index that is especially important for comparisons to the diseased state.

Improvement of Pain and Function by Using Botulinum Toxin Type A Injection in Patients with an Osteoarthritic Knee with Patellar Malalignment: An Electromyographic Study.

Objective: To determine the pain and electromyographic (EMG) amplitude ratio of the vastus medialis oblique (VMO) to the vastus lateralis (VL) after botulinum toxin type A (BTA) was injected in the bilateral osteoarthritic knee of patients with patellar malalignment for analysis. Material and methods: A total of fifteen patients were recruited; the more symptomatic knee of each patient received a BTA injection (BTA side). The other set of patients were left untreated. In all, fifteen healthy participants comprised the control group. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and numeric rating scale (NRS) for pain were assessed. The EMG amplitude of VL and VMO activity was recorded using an isokinetic dynamometer and synchronized using the BIOPAC MP100. The data were collected before and at 4, 8, and 12 weeks post−BTA injection. Results: The EMG ratios of the patient group were lower than those of the control group at all testing velocities (p < 0.05). The VMO/VL ratio improved significantly on the BTA side only. The VMO/VL ratios on the BTA side were higher than those on the untreated side (p < 0.05). Knee pain decreased significantly after the BTA injection. The EMG ratios were negatively correlated with the NRS and WOMAC scores. Conclusion: BTA injection effectively reduces knee pain and restores the EMG ratio between the VMO and VL.

Temporal modulation of H-reflex in young and older people: Acute effects during Achilles tendon vibration while standing.

Examining how timely is sensory input processed and regulated after a perturbation while standing, is a key element to understand postural control, especially in people with balance deficits, such as older adults. In this study, we investigated the age-related temporal modulations in spinal excitability, by measuring the soleus H-reflex within the first 250ms after switching on (V-ON) and off (V-OFF) a pair of vibrators, placed over the Achilles tendons. Twenty young (25.1±5.1yrs) and 16 older (71.8±6.1yrs) adults stood blindfolded, while 12-15s periods of Achilles tendon vibration (ATV) were applied with 20-24s intervals. Anterior/posterior center of pressure and electromyographic (EMG) responses [soleus (SOL) and tibialis anterior (TA)] were assessed whereas SOL H-reflex normalized to maximum M-wave (H/Mmax) and SOL EMG (H/SOL) were evaluated before ATV (Pre) and at 50, 100, 150, 200 and 250ms after the V-ON and V-OFF. Only in young adults the TA/SOL EMG ratio decreased 100 (p=0.032) and 150ms (p<0.001) after V-ON and the H/Mmax and H/SOL decreased 150-250ms after V-ON (p<0.001). At 50-250ms after V-OFF, H/Mmax was reduced compared to Pre values (p<0.001), with no differences between the age groups (p>0.05). H/SOL was decreased for the young adults (p<0.001) and remained reduced at least for the first 250ms after V-OFF. At 150ms after V-OFF, SOL/Mmax was decreased only for the older adults (p<0.001), whereas TA/SOL EMG gradually increased for both groups (p<0.001). When ATV is introduced while standing, the spinal excitability of older people is reduced later and to a lesser extent compared to young adults. Their limited capacity to down-regulate the "noisy" sensory input generated by ATV gives further evidence of a possible mechanism for their inefficient postural control.

Understanding Bench Press Biomechanics-Training Expertise and Sex Affect Lifting Technique and Net Joint Moments.

Mausehund, L and Krosshaug, T. Understanding bench press biomechanics-Training expertise and sex affect lifting technique and net joint moments. J Strength Cond Res 37(1): 9-17, 2023-The purpose of this study was to compare normalized net joint moments (NJMs), moment arms, and muscle activity in the bench press exercise between powerlifters and recreationally strength-trained lifters and between women and men. Thirty-four healthy adults, including 12 powerlifters (6 women and 6 men) and 22 recreational lifters (9 women and 13 men), performed a 6-8 repetition maximum set of the bench press, while elbow and shoulder NJMs and moment arms and electromyographic (EMG) activity of 6 upper extremity muscles were recorded. The results showed that training expertise and sex affected bench press technique substantially. Powerlifters applied a different bar path which impacted joint kinematics to a greater extent and joint kinetics to a lesser extent. Specifically, powerlifters had lower normalized peak elbow NJMs and shorter joint ROMs than recreational lifters ( p ≤ 0.05), yet no differences in normalized shoulder NJMs and muscle activity were observed. Women showed lower normalized mean shoulder NJMs, higher normalized peak elbow NJMs, and higher mean elbow to shoulder NJM ratios than men ( p ≤ 0.05). The muscle activity of the long head of the triceps brachii and the elbow to shoulder EMG ratio were higher, yet muscle activity of the sternocostal and abdominal head of the pectoralis major was lower for female than for male subjects ( p ≤ 0.05). In conclusion, powerlifters and men are more shoulder dominant when performing the bench press than recreational lifters and women, respectively. These findings will have implications for resistance training program design, expected training adaptations and bench press performance.

Effects of Clenching Strength on Exercise Performance: Verification Using Spinal Function Assessments.

This study aimed to determine the relationship between exercise performance and spinal function based on clenching strength. Low-intensity clenching contributes to joint movement, whereas high-intensity clenching contributes to joint fixation. Randomized crossover trial. Level 3. Two experiments were conducted using 2 groups of 20 healthy adults. The 4 clenching conditions in experiment 1 were 0%, 12.5%, 25%, and 50% of the maximum voluntary contraction (MVC) of the masseter muscle. Experiment 2 consisted of 3 conditions: no-bite condition, moderate effort, and maximum effort (max condition). In experiment 1, spinal function and ankle dorsiflexion tasks were measured for each clenching condition, and the ankle dorsiflexion task was measured in experiment 2. Regarding spinal function, we measured spinal reciprocal inhibition (RI) and excitability of spinal anterior horn cells. For the ankle dorsiflexion task, ankle dorsiflexion MVC was performed for 3 seconds under each clenching condition. The items analyzed were reaction time, peak ankle dorsiflexion torque, and soleus (Sol)/tibialis anterior (TA) electromyography (EMG) ratio. The results of experiment 1 illustrated that RI was significantly attenuated or eliminated with increasing clenching strength (>25% MVC). Spinal anterior horn cell excitability increased significantly with increasing clenching strength. The peak torque was significantly higher at 50% MVC than that at 0% MVC. In experiment 2, the peak torque was significantly higher under moderate and max conditions than no-bite condition, and the Sol/TA EMG ratio was significantly higher under max condition than that under moderate condition. The results illustrated that during high-strength clenching (≥50% MVC), antagonist muscles are activated simultaneously to increase muscle strength. High-strength clenching improved kinetic performance (joint fixation), whereas low-strength clenching (<50% MVC) enhanced exercise performance (joint movement).

Influence of success rate representation on the changes of performance and the corticospinal excitability accompany a short‐term motor skill learning of a coordinated upper limb movement in humans

Although it is known that motor performance improves through motor skill learning, it is unclear whether the success rate representation affects the motor performance in association with the corticospinal excitability changes through the learning process. By using transcranial magnetic stimulation (TMS), we examined the changes in the corticospinal excitability of the engaged muscles (first dorsal interosseous, extensor and flexor carpi radialis, and anterior deltoid, FDI, ECR, FCR, AD muscles) before and after a short-term learning of a dynamic and coordinated upper limb movement. The TMS coil was placed on the motor hots pot of the FDI muscle. Nineteen healthy volunteers using their dominant hand were asked to hold a pen and dot (black ink) the center of an A4-size paper at which a small red ink dot was printed. The subjects performed the trials at 1 Hz, and were asked to put their hand higher than 100 mm apart from the paper surface trial-by-trial. All subjects were divided into two groups; one engaged motor learning without success rate (SR) representation (control group) and other with (SR group). With the control group, 50 trials per session, totally 20 sessions were performed in the motor learning sessions by using the same papers. With the SR group, on the other hand, the performance before learning (50 trials) was assessed before the experiment on a separate day, and a circle with a diameter of which the length was calculated by the success rate of 60 percents according to the performance before learning (50 points distance from the target), was printed around the target red dot in the motor learning sessions. The changes in the performance, electromyography (EMG), and motor evoked potentials (MEP) to TMS before and after motor learning were analyzed. The results showed that the error from the target significantly decreased through the learning in both groups, and the success rate was significantly smaller in the SR group compared with that in the control group. The EMG activity of FDI muscle was smaller, and that of AD muscle was larger in the SR group than those in the control group, while difference in the EMGs showed nether in the ECR nor FCR muscle. Through learning, interestingly, MEP in the FDI muscle was significantly larger in the SR group than that in the control group at resting state, but no difference in the MEP between the groups during voluntary movements (motor task). Also, the MEP/Background EMG ratio showed no difference between the groups. Our results suggest that, in the motor learning the performance can be further improved by representing the success rate of the motor task, and that the central motor command emphasizing on the proximal rather than distal muscle may contribute to the improved performance.

An electromyographic and kinematic study of the scapular stabilisers.

BackgroundThe scapular stabilisers, especially the actions of the force couples around the scapula, have an impact on the biomechanics of the scapula and the orientation of the glenoid.ObjectivesThe aim of our study was to determine both the muscle activity and the correlation between the muscle activity ratio of the lower force couple (the serratus anterior lower fibres and the lower trapezius).MethodsThis was a quantitative cross-sectional study. Muscle activity of the dominant serratus anterior lower fibres and the lower trapezius muscles was collected with surface electromyographic (EMG) sensors and an inertial motion capture system was used to measure the three-dimensional (3D) shoulder flexion in the sagittal plane and abduction in the frontal plane. Graph Pad 5 (Prism, San Diego, CA, USA) was used for the statistical analysis. The confidence level was set at 95% (p < 0.05).ResultsSixteen men and women participated in our study, with a mean (standard deviation) age of 25.4 (± 4.6) years, weight of 80.2 (± 25.1) kg and height of 171.6 (± 10.3) cm. A strong negative correlation was found at the start of the abduction (r = −0.623; p = 0.01) between the muscle activity of the serratus anterior lower fibres and the lower trapezius.ConclusionsThe only significant increase in the mean EMG ratio of serratus anterior lower fibres versus the lower trapezius was present at 60% (from baseline) of abduction (p = 0.03).Clinical implicationsThe EMG activity ratio of serratus anterior lower fibres and lower trapezius remains variable in different movement planes.

Role of activation patterns of hip muscles in single-leg squats in healthy patients

Introduction:A risk factor for knee injuries is the medio-lateral displacement of the knee joint during a single-leg squat (SLS). It is to be supposed that different activation patterns of hip muscles are related to the medio-lateral displacement of the knee (1). Yet, little is known about the electromyographic (EMG) ratio between gluteus medius (GM) and the adductor muscles (ADD) at different knee flexion angles (2). Therefore, the EMG ratio between GM and ADD at different knee flexion angles was assessed during the SLS. These data should build a normative data base of healthy controls for getting in-sights on knee injury prevention.Hypotheses:The hypothesis was that according to different knee flexion angles, there is a variabil-ity of the EMG ratio between GM and ADD in healthy patients.Methods:A total of 17 healthy subjects (9 female/ 8 male, age of 25±4 years, BMI of 24±2 kg/m2) were included into the study. Exclusion criteria were Genu varum or Genu val-gum and pathologies which might affect coordination abilities of the lower extremities. Knee flexion angle was captured with a 3D motion analysis system (Vicon Motion Systems, Oxford,UK). Muscle activity of GM and ADD was measured by surface electromyography (Myon AG Schwarzener, CH). The EMG signal (10-500Hz band-pass filter, rectified, 250ms moving average) was normalized to maximum EMG am-plitude during a static maximum voluntary contraction against a handheld dynamome-ter (MicroFET2, Hoggan Scientific, UT, USA). The EMG ratio was defined as muscle activity of GM [%max] divided by muscle activity of ADD [%max]. Every participant did 12 single-leg squats on each side.Results:EMG ratio (median, interquartile range (25th - 75th quartile)) was calculated at the fol-lowing knee flexion angles (mean ± SD): EMG ratio at start position (11°±6°) = 2.5 (1.9 – 4.2), EMG ratio at 40° downward movement = 1.5 (1.1 – 2.7), EMG ratio at 60° downward movement = 1.2 (0.9 – 2.2), EMG ratio at maximum flexion angle (86°±16°) = 1.3 (0.9 – 1.9), EMG ratio at 60° upward movement = 2.0 (1.2 – 3.3), EMG ratio at 40° upward movement = 2.3 (1.5 – 4.4), EMG ratio at end position (8°±6°) = 3.2 (2.3 – 5.4).Conclusion:In the literature, the mean EMG ratios between GM and ADD at maximum knee flex-ion were ranged from 1.3 to 1.9 in healthy patients (3,4) and are comparable to our findings. The knee and hip have to be more stabilized during the upward movement by higher EMG ratios. The lower EMG ratio in the downward phase might be associated, amongst others, with the eccentrical deceleration movement. We assume that the consistently higher activation of the GM is attributed to its function as an essential hip stabilizer as well as to avoid a collapse in the knee joint in every single-leg situation. Therefore, we recommend hip abductor focused training to prevent knee injuries. Our results provide a basis for the comparison with patients and for the interpretation of medio-lateral displacements of the knee joint during a SLS.

Mind-Muscle Connection: Verbal Instructions Alter Electromyographic Activity for Elbow Flexors and Extensors During Co-Contraction Training.

Co-contraction training has demonstrated similar electromyographic (EMG) activity levels compared to conventional strength training. Since verbal instructions can increase EMG activity on target muscles during conventional exercises, the same should occur during co-contraction. In this study we analyzed whether different verbal instructions would alter the EMG activity of target muscles - biceps brachii (BB) and triceps brachii lateral head (TB) - during co-contraction training for the elbow joint. Seventeen males with experience in strength training performed a co-contraction set in two verbal instruction conditions to emphasize either elbow flexion or elbow extension. Surface electrodes were fixed over biceps brachii and triceps brachii lateral head muscles. We measured EMG mean amplitude and analyzed data with 2-way ANOVA. We found a significant interaction between muscle and verbal instruction (p = 0.002). Post hoc tests indicated that verbal instructions (p = 0.001) influenced the BB EMG activity (elbow flexion: M = 68.74, SD = 17.96%; elbow extension: M = 53.47, SD = 16.13%); and also showed difference (p = 0.006) in the EMG activity between BB and TB with verbal instruction emphasizing the elbow extension (BB: M = 53.47, SD = 16.13%; TB: M = 69.18, SD = 21.79%). There was a difference in the EMG ratio of BB/TB (p = 0.001) when focusing on elbow flexion (M = 1.09, SD = 0.30) versus elbow extension (M = 0.81, SD = 0.25). As verbal instruction modified the magnitude of muscle recruitment during co-contractions for elbow joint muscles, there is a clear mind-muscle connection of importance to this method of training. Also, of importance to trainers, verbal instructions seemed to affect individuals differentially.

The effect of 10 weeks of strength training on the electromyographic response of quadriceps portions

Abstract This study investigate the effect of 10-week strenght training on the amplitude of the electromyographic (EMG) signal of vastus medialis, vastus lateralis and rectus Femoris. Twenty three untrained volunteers performed 3-5 sets (3 sets - weeks 1 and 2; 4 series - weeks 3 and 4; 5 series weeks 5 to 10) with 6 repetitions, intensity of 50% of 1 repetition maximum (1RM), 3 min rest between sets and 6 s repetition duration at the knee extensor exercise. One group (5:1) performed concentric action of 5 s and eccentric of 1 s and the other (3:3) performed concentric of 3 s and eccentric of 3 s. The VM, VL and RF EMG (RMS) activities were recorded in each repetition of the three series at the first training session and the first three series at the last session. The protocol 5:1 led to EMG reduction in all portions, with a greater number of repetitions presenting differences at the VL and RF. VM and RF presented similar results at Group 3:3. It was verified that all the differences occurred in the second half of the series. It was also verified differences in EMG ratios just in group 3:3 and only in VM/VL and VM/RF. These results suggest that the coordination was not affected when equivalent repetitions of series were compared. It was also suggested that these results were influenced by the reduced degrees of freedom of the exercise and the training load progression adopted.

Comparison of Neuromuscular Firing Patterns of the Superficial Quadriceps in Soft Tissue Quadriceps Tendon Versus Bone-Patellar Tendon-Bone ACL Autografts.

Background:Soft tissue quadriceps tendon (QT) autografts are increasingly popular as a primary graft choice for anterior cruciate ligament reconstruction (ACLR), but no study has compared superficial quadriceps activity levels and leg extension strength for QT versus bone–patellar tendon–bone (BTB) autografts.Hypothesis:Harvesting the central portion of the QT will alter rectus femoris (RF) firing patterns during maximum voluntary isometric contraction.Study Design:Cohort study; Level of evidence, 3.Methods:A total of 34 patients (age range, 18-40 years) who underwent ACLR using a BTB (n = 17) or QT (n = 17) autograft at a single institution participated in this study. Participants, who had no neuromuscular injury or prior surgery on either lower extremity, were at least 1 year after ACLR, and were cleared for full activity. Postoperative rehabilitation protocols were consistent across participants. Synchronized electromyography (EMG) and isometric torque data were collected from participants in the seated position with the hips flexed to 90° and the knee at 60° of flexion. Participants were asked to extend their knees as quickly as possible and perform maximum voluntary isometric contraction for 3 seconds. A practice trial and 3 test trials were completed with 30-second rest intervals. Mixed (2 graft × 2 limb) analyses of variance were used to examine differences in average and peak torque values and RF/vastus lateralis (VL) and RF/vastus medialis (VM) ratios. Lysholm and International Knee Documentation Committee (IKDC) scores were compared between groups using unpaired t tests.Results:Significantly lower values were seen for the operative compared with the nonoperative extremity for average (P = .008; η2 = 0.201) and peak torque (P < .0001; η2 = 0.321), with no significant difference between graft types. Additionally, no significant differences in RF/VL or RF/VM ratios between limbs or graft types were observed.Conclusion:At 1 year after ACLR, QT and BTB autografts showed similar isometric strength deficits, with no differences in quadriceps muscle EMG ratios seen between the 2 graft types. The results support the use of a QT autograft for ACLR, as its graft harvest does not adversely affect quadriceps firing patterns in comparison with BTB graft harvest.

Extensor/flexor ratio of neck muscle strength and electromyographic activity of individuals with migraine: a cross-sectional study.

Neck pain is considered a common characteristic of migraine attacks. The relationship between neck pain and migraine can be explained by central sensitization of the trigeminocervical complex, where superior cervical afferents and the trigeminal nerve converge. However, few studies have evaluated motor control of cervical muscles in individuals with migraine. Thus, the purpose of the present study was to determine the extensor/flexor ratio of neck muscle strength and electromyographic activity during a test of maximal voluntary isometric contraction and craniocervical flexion in individuals with migraine and individuals without history of migraine or other headaches. Fifty-two women with the disease and 52 women with neither a history of migraine nor neck pain, between 18 and 55years old, were included in the study. The electromyographic activities of the sternocleidomastoid, anterior scalene, splenius capitis, and upper trapezius muscles were evaluated during a test of maximal voluntary isometric contraction and craniocervical flexion. The migraine group presented lower flexor muscle strength and a higher extensor/flexor muscle strength ratio than the control group. In addition, the migraine group showed a reduced electromyographic extensor/flexor muscle ratio during maximal voluntary isometric contraction in flexion. The results demonstrated worse performance in the craniocervical flexion test of the migraine group and a lower electromyographic ratio of extensor/flexor neck muscles in the last stage of the test. Altogether, the migraine group presented an imbalance in cervical muscles verified not only during force production, but also during muscle activity. These slides can be retrieved under Electronic Supplementary Material.

The effect of tactile and verbal guidance during scapulothoracic exercises: An EMG and kinematic investigation

BackgroundClinician-led training through tactile and verbal guidance to improve muscle activity and joint motion are a common but understudied focus of therapeutic interventions for shoulder pain. The purpose of this study was to determine if clinician guidance changes scapulothoracic muscle activity and kinematics compared to unguided shoulder exercises. MethodsEleven participants with shoulder pain were studied. Electromyographic (EMG) sensors were placed on the serratus anterior and upper and lower trapezii. Scapulothoracic and sternoclavicular kinematics were collected using electromagnetic sensors. Five common resisted shoulder exercises were performed with the following guidance: unguided, combined (verbal and tactile cues), and verbal guidance only. One-way repeated measures ANOVAs determined the effect of guidance versus unguided conditions for each exercise. ResultsNine of ten combinations of exercise and guidance techniques demonstrated a significant effect of guidance for either muscle activity or joint kinematics. The guidance condition with the most frequent significant improvements across all variables was the combined condition. The exercises with the most frequent significant improvements across all variables were the external rotation exercises. Variables improved most frequently were: upper:lower trapezius EMG ratio (up to 11%), sternoclavicular elevation (up to 6°) and scapulothoracic internal rotation positioning (up to 8°), and sternoclavicular retraction displacement (up to 5°). ConclusionShoulder muscle activity and kinematics during exercises can be modified by tactile and verbal guidance. Most improvements in muscle activity occurred with verbal guidance during external rotation exercises. Most improvements in joint positioning and movement occurred with combined guidance during external rotation exercises.

Mirror movements in children with unilateral cerebral palsy due to perinatal stroke: clinical correlates of plasticity reorganization.

We aimed to determine if the mirror movements that often result in children with unilateral cerebral palsy (CP) after perinatal stroke represent a clinical biomarker of developmental plasticity. This was a prospective, controlled cohort study. Mirror movements in children with unilateral CP from a population-based cohort were compared to those of typically developing controls. The population with stroke was assessed further via electromyography (EMG), motor function, and corticospinal organization investigations. Mirror movements were quantified (0-5) bidirectionally. EMG mirror movements were quantified during voluntary contraction. Motor function was quantified by validated measures including the Assisting Hand Assessment (AHA). Corticospinal organization was categorized as ipsilateral or contralateral using transcranial magnetic stimulation (TMS). The relationships between mirror movements, function, and corticospinal organization were assessed (t-tests, Pearson rank correlation coefficients). Ninety-two participants were scored (55 males, 37 females, mean [SD] 12y [5y 6mo], range 4-17y), 63 with complete motor outcomes and 39 with TMS data. EMG ratios correlated with clinical mirror movements (r=0.562, p=0.008). Mild mirror activity in controls declined with age (r=-0.459, p<0.001). Mirroring was stronger with tasks performed by the affected hand (p<0.001). Mirror movements correlated with AHA scores (r=-0.255, p=0.04) and poor motor outcome (p<0.001). Unaffected hand mirror activity was higher in children with ipsilateral corticospinal tract arrangements (p<0.001). Clinical mirror movements correlate with disability and corticospinal organization in children with unilateral CP with perinatal stroke. This simple bedside biomarker could facilitate patient selection for personalized rehabilitation. Mirror movements are a clinical indicator of corticospinal organization in children with unilateral cerebral palsy with perinatal stroke. Mirroring is strongest in children with ipsilateral corticospinal tract reorganization. The concept of a 'directionality factor' to mirror movements highlights additional, clinically relevant functional correlations.

Force direction and arm position affect contribution of clavicular and sternal parts of pectoralis major muscle during muscle strength testing

Study DesignCross-sectional study. Purpose of the StudyThe study aims to determine the effects of force direction and arm position in differentiating the clavicular (PMc) and sternal (PMs) parts of the pectoralis major (PM) muscle during maximal voluntary isometric contraction (MVIC) to provide basic evidence to support the clinical thinking behind muscle strength testing of PM. MethodsNine experimental conditions with 3 force directions of horizontal adduction (+30° oblique, horizontal, and −30° oblique to the transverse plane) and 3 arm rotation positions (0°, 45°, and 90° shoulder external rotation from the transverse plane) were randomly tested for 26 healthy male participants. The MVIC force level was monitored and measured with a fixed dynamometer, and the surface electromyographic (EMG) signals of the PMc, PMs, anterior deltoid, middle deltoid, and latissimus dorsi were collected during the test for each condition. The PMc/PMs EMG ratio and normalized EMG amplitude were used to quantify the contribution of the tested muscles. ResultsThe MVIC force level significantly declined when the arm's external rotation increased (P < .01; the grand mean decreased from 106.7 N ± 27.8 N to 89.5 N ± 22.6 N). The PMc/PMs EMG ratio showed that the best test condition to differentiate the PMc and PMs was the force direction of +30° oblique to the transverse plane and the 45° arm rotation position. Other muscles contributed less than 40% of their MVIC activity levels, with a higher activation level found in the anterior deltoid muscle (P < .01). ConclusionsArm rotation position should be considered as a predominant factor when clinically examining the strength of horizontal adduction movement. All tested conditions failed to fully separate PMc and PMs activation during MVIC and suggested that functional differentiation of the PM might not be applicable to maximal exertion. Level of EvidenceNA.

Orthotic bicycle shoe insoles show no effects on leg muscle activation patterns or performance in recreational cyclists

This study tested the hypothesis that an orthotic insole in cycling shoes would stabilize pedalling mechanics, reduce or alter activity of the quadriceps and hamstring muscles, and reduce physiological work while cycling. Nine cyclists were evaluated during four VO2max tests, using four different insole conditions (flat (no insole), low, medium, and high arch supports) in a random order. Wireless electromyography (EMG) was used to measure muscle activity, and telemetry-based gas analysis and power output to determine cycling efficiency. The non-flat insole that resulted in the lowest level of lateral knee movement was identified as ‘best fit’. General linear mixed models were run two ways, with the most effective insole for the dominant leg and non-dominant leg identified as the overall ‘best fit’ insoles. There was an interaction for the dominant leg hamstrings EMG ratio among insoles and pedal float type (p = .007). Heart rate at anaerobic threshold was reduced by best fit insoles for the dominant leg (p = .014) and non-dominant leg (p = .017); this may be the result of hydration status or existing fatigue. The results indicate that arch support alone does not have an effect on mediolateral EMG ratios of the quadriceps or hamstrings, or performance. Further investigation of insole effects on muscle activation patterns is warranted.